JP6887814B2 - Magnetic recording medium and magnetic storage device - Google Patents

Description

The present invention relates to a magnetic recording medium and a magnetic storage device.

In recent years, the demand for larger capacities for hard disk devices has become stronger and stronger.

However, with the current recording method, it has become difficult to improve the recording density of the hard disk device.

The heat-assisted magnetic recording method is one of the technologies that have been actively researched and attracted attention as a next-generation recording method. The heat-assisted magnetic recording method is a recording method in which a magnetic head irradiates a magnetic recording medium with near-field light to locally heat the surface of the magnetic recording medium to reduce the coercive force of the magnetic recording medium for writing. ..

In the heat-assisted magnetic recording method, as the material constituting the magnetic layer, L1 ₀ type FePt having a crystalline structure ^{(Ku~7 × 10 7 erg / cm} 3), CoPt (Ku~5 × 10 having an L1 ₀ type crystal structure High Ku materials such as ⁷ erg / cm ^{3) are used.}

When a high Ku material is used as the material constituting the magnetic layer, KuV / kT becomes large. Here, Ku is the magnetic anisotropy constant of the magnetic particles, V is the volume of the magnetic particles, k is the Boltzmann constant, and T is the temperature. Therefore, the volume of the magnetic particles can be reduced without aggravating the thermal fluctuation. At this time, by making the magnetic particles finer, in the heat-assisted magnetic recording method, the transition width can be narrowed, so that noise can be reduced and the signal-to-noise ratio (SNR) can be improved.

In addition, the perpendicular magnetic anisotropy obtain high heat-assisted magnetic recording medium, it is necessary to alloy (001) orientation having an L1 ₀ type crystal structure used as a material constituting a magnetic layer. Here, since the (001) orientation of the magnetic layer is controlled by the base layer, it is necessary to appropriately select the material constituting the base layer.

Conventionally, MgO, CrN, TiN and the like have been known as materials constituting the base layer of the heat-assisted magnetic recording medium.

For example, Patent Document 1, to prepare a base layer mainly composed of MgO, discloses a further method of manufacturing an information recording medium to produce an L1 ₀ form ordered alloy layer consisting of FePt alloy.

Further, Patent Document 2, as a base layer, the main component W, and, B, Si, C, or, a crystalline underlayer containing oxide, and a main component an alloy having an L1 ₀ structure A magnetic recording medium having a magnetic layer and a magnetic layer is disclosed.

Further, in Patent Document 3, as a temperature control layer of a heat-assisted magnetic recording medium, a high thermal conductivity material that separates a region of a low thermal conductivity material extending through a film thickness and a region of a low thermal conductivity material. It is disclosed to use a thin film containing a continuous matrix as a region.

Japanese Unexamined Patent Publication No. 11-353648 Japanese Unexamined Patent Publication No. 2014-220029 Japanese Unexamined Patent Publication No. 2006-196151

The thermally assisted magnetic recording medium, in order to obtain a good magnetic recording characteristics, as described above, by using a particular base layer to an alloy having an L1 ₀ type crystal structure forming the magnetic layer (001) orientation It is necessary.

However, in the conventional technique, the (001) orientation of the magnetic layer is insufficient, so that a base layer capable of improving the (001) orientation of the magnetic layer of the heat-assisted magnetic recording medium has been required. ..

Further, the base layer of the heat-assisted magnetic recording medium is required to function as a temperature control layer. That is, when the heat-assisted magnetic recording medium is irradiated with near-field light to locally heat the surface of the heat-assisted magnetic recording medium, the expansion of the heating spot is suppressed to narrow the magnetization transition region in the plane direction. , It has been required to reduce noise, that is, to increase the signal-to-noise ratio (SNR).

In view of the above circumstances, an object of the present invention is to provide a magnetic recording medium having a high signal-to-noise ratio (SNR).

(1) a substrate, an underlayer, a magnetic layer comprising an alloy having an L1 ₀ type crystal structure which is oriented (001), comprising in this order, the underlying layer from the side of the substrate, first The base layer and the second base layer are included in this order, the first base layer is a crystalline layer containing Mo as a main component, and the second base layer contains Mo as a main component. It is a crystalline layer containing the material and the oxide to be used, and the content of the oxide is in the range of 2 mol% to 30 mol%, and the oxide is an oxide of Mo. Magnetic recording medium.
( 2 ) The magnetic recording medium according to (1), wherein the second base layer has a non-granular structure.
( 3 ) A barrier layer is further included between the base layer and the magnetic layer, and the barrier layer is derived from MgO, TiO, NiO, TiN, TaN, HfN, NbN, ZrC, HfC, TaC, NbC, TiC. The magnetic recording medium according to (1) or (2) , which comprises one or more selected from the group and has a NaCl type structure.
( 4 ) An orientation control layer is further included between the substrate and the base layer, and the orientation control layer has a Cr layer having a BCC structure, an alloy layer containing Cr as a main component, or a B2 structure. the magnetic recording medium according to any one of to, characterized in that an alloy layer (1) to (3) having.
(5) (1) to (4) a magnetic storage apparatus comprising a magnetic recording medium according to any one of.

According to the present invention, it is possible to provide a magnetic recording medium having a high signal-to-noise ratio (SNR).

It is a schematic diagram which shows an example of the magnetic recording medium of this embodiment. It is a schematic diagram which shows an example of the magnetic storage device of this embodiment. It is a schematic diagram which shows an example of the magnetic head of FIG.

Hereinafter, embodiments for carrying out the present invention will be described, but the present invention is not limited to the following embodiments, and various modifications and variations to the following embodiments are made without departing from the scope of the present invention. Substitutions can be added.

(Magnetic recording medium)
FIG. 1 shows an example of the magnetic recording medium of the present embodiment.

The magnetic recording medium 100 includes a substrate 1, an underlayer 2, a magnetic layer 3 containing an alloy having an L1 ₀ type crystal structure which is oriented (001), in this order. The base layer 2 includes the first base layer 4 and the second base layer 5 in this order from the side of the substrate 1. The first base layer 4 is a crystalline layer containing Mo as a main component. The second base layer 5 is a crystalline layer containing a material containing Mo as a main component and an oxide, and the content of the oxide is in the range of 2 mol% to 30 mol%. The oxide is an oxide of one or more elements selected from the group consisting of Cr, Mo, Nb, Ta, V, and W.

By adopting such a configuration, the magnetic recording medium 100 has a high SNR.

The reason why the SNR of the magnetic recording medium 100 is high will be described below.

First, Mo contained in the base layer 2 is a cubic lattice (BCC) structure body centered, (100) because of high orientation, the alloy having an L1 ₀ type crystal structure constituting the magnetic layer 3 (001) orientation It is possible to increase. Further, the oxide contained in the second base layer 5 can enhance the lattice consistency between the second base layer 5 and the magnetic layer 3 without impairing the crystallinity and (100) orientation of Mo. Is possible. Further, when writing is performed by locally heating the surface of the magnetic recording medium 100 to reduce the coercive force of the magnetic layer 3, the base layer 2 suppresses the spread of the heating spot, thereby causing a magnetization transition in the plane direction. The area can be narrowed.

The magnetic recording medium 100 will be described in more detail.

In the magnetic recording medium 100, the base layer 2 has a two-layer structure, and the first base layer 4 and the second base layer 5 are provided in this order from the side of the substrate 1. As described above, the second base layer 5 is a crystalline layer containing a material containing Mo as a main component, and since it has high (100) orientation, it is formed on it (001) oriented. to the magnetic layer 3 is lattice-matched comprising an alloy having a by and L1 ₀ type crystal structure. Then, by providing a crystalline layer containing Mo as a main component as the first base layer 4 under the second base layer 5, the crystallinity and (100) orientation of the second base layer 5 Can be further enhanced.

In the heat-assisted magnetic recording medium, it is necessary to suppress the expansion of the heating spot in order to narrow the magnetization transition region in the plane direction and reduce the noise of the magnetic recording medium. Therefore, for example, as described in Patent Document 3, the base layer is divided into a region of a columnar high thermal conductivity material (for example, metal) perpendicular to the surface of the substrate and a low thermal conductivity that separates the region. When the material (for example, oxide) is composed of a so-called granular structure, heat retention occurs at the interface of the columnar region, so that it is possible to suppress the lateral expansion of the heating spot.

On the other hand, the second base layer 5 does not have to have a structure in which a region of a large columnar high thermal conductivity material is separated by a region of a thick low thermal conductivity material like a granular structure, and has a thin oxide grain boundary. It is preferable that the columnar crystal grains have a non-granular structure in which the columnar crystal grains are partially connected to each other.

In such a non-granular structure, when the same volume of oxide is contained, the pitch of the oxide grain boundaries becomes finer due to the thinner oxide layer where heat retention occurs as compared with the conventional granular structure, and the columns are columnar. Since the structure contains a large amount of grain boundaries of crystal grains and oxides per unit length, the effect of suppressing the spread of heating spots is enhanced. When such a configuration is adopted, since the specific surface area of the columnar crystal grains becomes large, the effect of partial reduction of the oxide during film formation becomes more remarkable than that of a general granular structure, but it is included in the second base layer 5. Since the metal element constituting the oxide can be completely dissolved in the crystal grains of the material containing Mo as a main component, it is possible to prevent the crystal grains from being lowered in crystallinity.

In the present specification and claims, the crystalline layer containing Mo as a main component means a crystalline layer having a Mo content of 50 at% or more. At this time, the Mo content of the crystalline layer containing Mo as a main component is preferably 80 at% or more, and more preferably 100 at%.

The crystalline layer containing Mo as a main component is not particularly limited, but is a Mo layer, a Mo-W layer, a Mo-Cu layer, a Mo-Ni layer, a Mo-Fe layer, a Mo-Re layer, and a Mo-C layer. And so on.

Further, in the present specification and claims, the material containing Mo as a main component means a material having a Mo content of 50 at% or more. At this time, the Mo content of the material containing Mo as the main component is preferably 70 at% or more, more preferably 90 at% or more.

The material containing Mo contained in the second base layer 5 as a main component is not particularly limited, but Mo, Mo-W, Mo-Cu, Mo-Ni, Mo-Fe, Mo-Re, Mo-C, etc. Can be mentioned.

The second base layer 5 is a crystalline layer containing an oxide in the range of 2 mol% to 30 mol%.

The oxide is an oxide of one or more elements selected from the group consisting of Cr, Mo, Nb, Ta, V, and W.

The oxide is not particularly limited, but is CrO, Cr ₂ O ₃ , CrO ₃ , MoO ₂ , MoO ₃ , Nb ₂ O ₅ , Ta ₂ O ₅ , V ₂ O ₃ , VO ₂ , WO ₂ , WO ₃ , WO _{6 and the} like can be mentioned. Of these, Mo oxide is the most preferable. This is because Mo, which is produced by partially reducing the oxide of Mo, can be dissolved in the crystal grains of the material containing Mo as the main component, which constitutes the second base layer 5, at a total rate of solid solution particularly easily. ..

The oxide is not limited to these, and may be a reduced product, a mixture, or a composite oxide thereof.

In the present embodiment, the oxide content of the second base layer 5 is in the range of 2 mol% to 30 mol%, and preferably in the range of 10 mol% to 25 mol%. When the oxide content of the second base layer 5 exceeds 30 mol%, the (100) orientation of the second base layer 5 is lowered, and when it is less than 2 mol%, the (001) of the magnetic layer 3 is reduced. ) The effect of increasing orientation cannot be exhibited.

In this embodiment, the alloy having an L1 ₀ type crystal structure in the magnetic layer 3, the magnetic anisotropy constant Ku is high.

As an alloy having an L1 ₀ type crystal structure, for example, FePt alloys, CoPt alloys.

When forming the magnetic layer 3, in order to promote the ordering of the alloy having an L1 ₀ type crystal structure, it is preferable to heat treatment. In this case, in order to reduce the heating temperature (ordering temperature), the alloy having an L1 ₀ type crystal structure, Ag, Au, Cu, may be added to Ni or the like.

The crystal grain of the alloy having an L1 ₀ type crystal structure in the magnetic layer 3 is preferably is isolated magnetically. Therefore, the magnetic layer 3 includes SiO ₂ , TiO ₂ , Cr ₂ O ₃ , Al ₂ O ₃ , Ta ₂ O ₅ , ZrO ₂ , Y ₂ O ₃ , CeO ₂ , MnO, TiO, ZnO, B ₂ O ₃ , C, B, BN preferably further contains one or more substances selected from the group. As a result, the exchange bond between the crystal grains can be more reliably divided, and the SNR of the magnetic recording medium 100 can be further increased.

In the present embodiment, it is preferable that the second base layer 5 has a non-granular structure. As described above, the second base layer 5 is a layer having a function of suppressing the lateral spread of the heating spot. For that purpose, instead of a structure in which large columnar metal crystal grains are separated by a thick oxide layer as in the so-called granular structure, a structure in which columnar crystal grains are partially connected via thin oxide grain boundaries is adopted. Is preferable.

As a method of forming the second base layer 5 having a non-granular structure by using a sputtering method, a method of introducing oxygen into a sputtering gas to perform reactive sputtering, a method of reducing the amount of oxide contained in the target, and the like, are used. Examples thereof include a method of reducing the particle size of the oxide and a method of using an oxide that is easily reduced.

In the present embodiment, the barrier layer 6 is provided between the base layer 2 and the magnetic layer 3.

The barrier layer 6 contains one or more selected from the group consisting of MgO, TiO, NiO, TiN, TaN, HfN, NbN, ZrC, HfC, TaC, NbC, and TiC, and has a NaCl type structure.

In the present embodiment, as the magnetic layer 3, (001) uses a magnetic layer which comprises an alloy having an orientation to have L1 ₀ type crystal structure, to promote the ordering of the alloy having an L1 ₀ type crystal structure, magnetic When forming the layer 3, the substrate 1 may be heated. The barrier layer 6 is a layer provided to suppress interfacial diffusion between the base layer 2 and the magnetic layer 3 at this time.

The thickness of the barrier layer 6 is preferably in the range of 0.5 nm to 10 nm. When the thickness of the barrier layer 6 is 0.5 nm or more, it becomes easy to suppress the interfacial diffusion between the base layer 2 and the magnetic layer 3 when the substrate 1 is heated. Further, when the thickness of the barrier layer 6 is 10 nm or less, heat is easily conducted from the magnetic layer 3 to the second base layer 5.

In the present embodiment, between the substrate 1 and the base layer 2, as the orientation control layer 7, a Cr layer having a BCC structure, an alloy layer containing Cr as a main component, or an alloy layer having a B2 structure is formed. It is provided. The orientation control layer 7 is a layer provided to ensure that the orientation of the base layer 2 provided on the base layer 2 is (100) oriented. Therefore, it is preferable that the orientation control layer 7 is also (100) oriented.

In the present specification and claims, the alloy containing Cr as a main component means an alloy having a Cr content of 50 at% or more. At this time, the Cr content of the alloy containing Cr as a main component is preferably 70 at% or more, more preferably 90 at% or more.

The alloy containing Cr as a main component is not particularly limited, and examples thereof include CrMn alloys, CrMo alloys, CrW alloys, CrV alloys, CrTi alloys, and CrRu alloys.

Further, if elements such as B, Si, and C are added to the alloy containing Cr as a main component, the crystal particle size, the degree of dispersion, and the like of the base layer 2 can be further improved. However, when these elements are added, it is preferable to add them within a range in which the crystallinity of the orientation control layer 7 does not deteriorate.

Examples of alloys having a B2 structure include RuAl alloys and NiAl alloys.

A carbon protective layer 8 and a lubricating layer 9 made of a perfluoropolyether-based fluororesin are provided on the magnetic layer 3.

Known carbon protective layers 8 and lubricating layers 9 can be used.

The barrier layer 6, the orientation control layer 7, the carbon protective layer 8, and the lubricating layer 9 may be omitted if necessary.

Further, in order to cool the magnetic layer 3 quickly, a heat sink layer may be further provided on the magnetic recording medium 100.

For the heat insulating layer, an alloy containing a metal having a high thermal conductivity such as Ag, Cu, Al, and Au or a metal having a high thermal conductivity such as Ag, Cu, Al, and Au as a main component can be used.

The heat sink layer can be provided, for example, under the orientation control layer 7 or between the orientation control layer 7 and the barrier layer 6.

Further, in order to improve the writing characteristics, the magnetic recording medium 100 may be further provided with a soft magnetic layer.

The material constituting the soft magnetic layer is not particularly limited, but is an amorphous alloy such as CoTaZr alloy, CoFeTaB alloy, CoFeTaSi alloy, CoFeTaZr alloy, microcrystalline alloy such as FeTaC alloy and FeTaN alloy, and polycrystal such as NiFe alloy. Alloys can be used.

The soft magnetic layer may be a single-layer film or a laminated film having an antiferromagnetic bond with a Ru layer having an appropriate film thickness interposed therebetween.

In addition to the above-mentioned layers, a seed layer, an adhesive layer, and the like can be further provided on the magnetic recording medium 100, if necessary.

(Magnetic storage device)
A configuration example of the magnetic storage device of this embodiment will be described.

The magnetic storage device of the present embodiment includes the magnetic recording medium of the present embodiment.

The magnetic storage device may have, for example, a configuration having a magnetic recording medium driving unit for rotating the magnetic recording medium and a magnetic head having a near-field light generating element at the tip portion. Further, the magnetic storage device includes a laser generating unit for heating the magnetic recording medium, a waveguide for guiding the laser light generated from the laser generating unit to the near-field light generating element, and a magnetic head drive for moving the magnetic head. It can further have a unit and a recording / playback signal processing system.

FIG. 2 shows an example of the magnetic storage device of the present embodiment.

The magnetic storage device shown in FIG. 2 includes a magnetic recording medium 100, a magnetic recording medium driving unit 101 for rotating the magnetic recording medium 100, a magnetic head 102, and a magnetic head driving unit 103 for moving the magnetic head. , The recording / playback signal processing system 104 is included.

FIG. 3 shows an example of the magnetic head 102.

The magnetic head 102 includes a recording head 208 and a reproduction head 211.

The recording head 208 transmits the main magnetic pole 201, the auxiliary magnetic pole 202, the coil 203 for generating a magnetic field, the laser diode (LD) 204 serving as a laser generator, and the laser light 205 generated from the LD to the near-field light generating element 206. It has a waveguide 207 for the purpose.

The reproduction head 211 has a reproduction element 210 sandwiched between shields 209.

Since the magnetic storage device shown in FIG. 2 uses the magnetic recording medium 100, it is possible to increase the SNR and provide a magnetic storage device having a high recording density.

Specific examples will be described below, but the present invention is not limited to these examples.

(Example 1)
A magnetic recording medium (see FIG. 1) was prepared. The manufacturing process of the magnetic recording medium will be described below.

After forming a Cr-50at% Ti (alloy with a Cr content of 50at% and a Ti content of 50at%) having a film thickness of 25 nm on a glass substrate 1 having an outer diameter of 2.5 inches as a seed layer. , The substrate 1 was heated at 300 ° C. Then, as the orientation control layer 7, a Cr-5at% Mn (alloy having a Cr content of 95 at% and a Mn content of 5 at%) having a film thickness of 20 nm was formed. Next, a Mo layer having a film thickness of 20 nm is formed as the first base layer 4, and Mo-3.3MoO having a non-granular structure having a film thickness of 20 nm is formed as the second base layer 5 on the first base layer 4. _A film 3 (alloy having a Mo content of 96.7 mol% and a MoO ₃ content of 3.3 mol%) was formed. Further, as the barrier layer 6, an MgO film having a film thickness of 2 nm was formed. Then, by heating the substrate 1 at 580 ° C., as the magnetic layer 3, the thickness of _{10nm (Fe-45at% Pt)} -12mol% SiO 2 -6mol% BN ( content of Fe 55 at%, the content of Pt 45at% An alloy having an alloy content of 82 mol%, a SiO ₂ content of 12 mol%, and a BN content of 6 mol%) was formed. Further, after forming the carbon protective layer 8 having a film thickness of 3 nm, a lubricating layer 9 made of a perfluoropolyether-based fluororesin was formed on the surface of the carbon protective layer 8 to prepare a magnetic recording medium.

(Examples 2 to 4)
A magnetic recording medium was produced in the same manner as in Example 1 except that the composition of the second base layer 5 _{was changed to Mo-7.1MoO 3} , Mo-16.9MoO ₃ , and Mo-23.3MoO _{3, respectively.} did.

(Examples 5 to 9)
The composition of the second base layer 5, respectively _{Mo-16.9Cr 2 O 3, Mo} -16.9WO 2, Mo-16.9Nb 2 O 5, Mo-16.9Ta 2 O 5, Mo-16.9V It was changed to ₂ O _3, in the same manner as in example 1 to prepare a magnetic recording medium.

(Example 10)
A magnetic recording medium was produced in the same manner as in Example 3 except that the composition of the first base layer 4 was changed to Mo-10W (alloy having a Mo content of 90 at% and a W content of 10 at%). did.

(Examples 11 and 12)
The composition of the second base layer 5 is Mo-10W-16.9MoO ₃ (alloy with Mo content 74.1 mol%, W content 10 mol%, MoO _{3 content 16.9 mol%) and Mo.} -8MoO ₂ -8MoO ₃ except for changing the (content of Mo 84 mol%, content of 8 mol% of MoO _2, MoO ₃ content 8 mol% of the alloy), in the same manner as in example 1, a magnetic recording medium Made.

(Comparative Example 1)
A magnetic recording medium was produced in the same manner as in Example 1 except that the second base layer 5 was not formed.

(Comparative Example 2)
A magnetic recording medium was produced in the same manner as in Example 1 except that the first base layer 4 was not formed.

(Comparative Examples 3 and 4)
A magnetic recording medium was produced in the same manner as in Example 1 except that the composition of the second base layer 5 _{was changed to Mo-1.6MoO 3} and Mo-31.3MoO _{3, respectively.}

(Comparative Example 5)
The composition of the second base layer 5 was changed to Mo-7.9SiO ₂ (alloy having a Mo content of 92.1 mol% and a SiO ₂ content of 7.9 mol%) in the same manner as in Example 1. , A magnetic recording medium was prepared.

(Comparative Example 6)
A magnetic recording medium was produced in the same manner as in Comparative Example 5 except that the first base layer 4 was not formed.

(Comparative Examples 7-9)
Magnetic recording in the same manner as in Example 1 except that the composition of the second base layer 5 _{was changed to Mo-15.3TIO, Mo-15.3B 2} O ₃ , and Mo-15.3 Al ₂ O _{3, respectively.} A medium was prepared.

Next, the half width of the Mo (200) peak, the half width of the FePt (200) peak, CTTG and SNR were evaluated.

(Half width of Mo (200) peak)
Using an X-ray diffractometer (manufactured by Philips), the X-ray diffraction spectrum of the intermediate sample of the magnetic recording medium formed up to the base layer 2 was measured, and the half width of the Mo (200) peak was determined.

The orientation of (100) in the base layer 2 was evaluated using the (200) peak of Mo contained in the base layer 2, that is, the half width of the Mo (200) peak. Here, since the Mo (200) peak has high intensity and is easy to analyze, the peak of the Mo (200) plane, which is a plane parallel to the Mo (100) plane, was used.

(Half width of FePt (200) peak)
Using an X-ray diffractometer (manufactured by Philips), the X-ray diffraction spectrum of the intermediate sample of the magnetic recording medium formed up to the magnetic layer 3 was measured, and the half width of the FePt (200) peak was determined.

Incidentally, (001) orientation of the magnetic layer 3, (200) peak of the FePt alloy having an L1 ₀ type crystal structure of the magnetic layer 3, i.e., was evaluated using the half-width of the FePt (200) peak. Here, the (001) peak of the FePt alloy, that is, the FePt (001) peak does not have a sufficiently large appearance angle 2θ. Therefore, even if the low angle side is widened to the measurement limit when measuring the locking curve, the intensity of the FePt (001) peak is not stable with respect to the case where there is no peak, and it is difficult to analyze the half width. Is. For such device measurement reasons, it is difficult to evaluate the (001) orientation of the magnetic layer 3 using the full width at half maximum of the FePt (001) peak. On the other hand, the FePt (200) peak appears when the FePt alloy is oriented (001), but since the appearance angle 2θ is sufficiently large, it is suitable for evaluating the (001) orientation of the magnetic layer.

(CTTG)
The CTTG (Cross-Track Thermal Gradient) of the magnetic recording medium was measured using the read / write analyzer RWA1632 and the spin stand S1701MP (all manufactured by GUZIK). Here, CTTG has a thermal gradient [K / nm] in the direction perpendicular to the track direction, and the larger the value, the steeper the thermal gradient, that is, the larger the difference in recording temperature between the recording bits. It shows that there is little bleeding.

In the magnetic recording media of Comparative Examples 2 and 6, the recorded signal strength was weak and the writing line width could not be specified, so that CTTG could not be measured.

(SNR)
Using the magnetic head 102 (see FIG. 3), an all-one pattern signal having a line recording density of 1500 kFCI was recorded on a magnetic recording medium, and the SNR was measured. Here, the power applied to the laser diode was adjusted so that the track width MWW defined as the half width of the track profile was 60 nm.

Table 1 shows the evaluation results of the half width of the Mo (200) peak, the half width of the FePt (200) peak, and CTTG and SNR.

From Table 1, it can be seen that the magnetic recording media of Examples 1 to 12 have a higher CTTG and a higher SNR than the magnetic recording media of Comparative Examples 1 to 3 and 6 to 9. Further, since the magnetic recording media of Examples 1 to 4 and 10 to 12 have a second base layer 5 containing an oxide of Mo, the CTTG and SNR are particularly high.

On the other hand, as the grain boundaries of the oxide increase, the heat becomes less likely to spread, so that the CTTG may increase depending on the amount and type of the oxide, as in the magnetic recording media of Comparative Examples 4 and 5. However, the SNR includes factors such as the orientation of the base layer 2 and the magnetic layer 3 in addition to the CTTG. Therefore, in the magnetic recording media of Comparative Examples 4 and 5, the orientation of the base layer and the magnetic layer is lost, and the SNR is low.

1 Substrate 2 Underlayer 3 Magnetic layer 4 First underlayer 5 Second underlayer 6 Barrier layer 7 Orientation control layer 8 Carbon protective layer 9 Lubricant layer 100 Magnetic recording medium 101 Magnetic recording medium drive unit 102 Magnetic head 103 Magnetic head Drive unit 104 Recording / playback signal processing system 201 Main magnetic pole 202 Auxiliary magnetic pole 203 Coil 204 Laser diode 205 Laser light 206 Proximity field light generating element 207 Waveguide 208 Recording head 209 Shield 210 Reproduction element 211 Reproduction head 212 Magnetic recording medium

Claims (5)

A substrate, an underlayer, a magnetic layer comprising an alloy having an L1 ₀ type crystal structure which is oriented (001), comprising in this order,
The base layer includes a first base layer and a second base layer in this order from the side of the substrate.
The first base layer is a crystalline layer containing Mo as a main component.
The second base layer is a crystalline layer containing a material containing Mo as a main component and an oxide, and the content of the oxide is in the range of 2 mol% to 30 mol%.
A magnetic recording medium characterized in that the oxide is an oxide of Mo. The magnetic recording medium according to claim 1, wherein the second base layer has a non-granular structure. A barrier layer is further included between the base layer and the magnetic layer.
The barrier layer contains at least one selected from the group consisting of MgO, TiO, NiO, TiN, TaN, HfN, NbN, ZrC, HfC, TaC, NbC, and TiC, and has a NaCl type structure. The magnetic recording medium according to claim 1 or 2. An orientation control layer is further included between the substrate and the base layer.
The aspect according to any one of claims 1 to 3 , wherein the orientation control layer is a Cr layer having a BCC structure, an alloy layer containing Cr as a main component, or an alloy layer having a B2 structure. The magnetic recording medium described. A magnetic storage device including the magnetic recording medium according to any one of claims 1 to 4.

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